1. Field of Inventions
The present inventions relate generally to structures for positioning diagnostic and therapeutic elements within the body and, more particularly, to devices which are particularly well suited for the treatment of cardiac conditions.
2. Description of the Related Art
There are many instances where diagnostic and therapeutic elements must be inserted into the body. One instance involves the treatment of cardiac conditions such as atrial fibrillation and atrial flutter which lead to an unpleasant, irregular heart beat, called arrhythmia.
Normal sinus rhythm of the heart begins with the sinoatrial node (or “SA node'”) generating an electrical impulse. The impulse usually propagates uniformly across the right and left atria and the atrial septum to the atrioventricular node (or “AV node”). This propagation causes the atria to contract in an organized way to transport blood from the atria to the ventricles, and to provide timed stimulation of the ventricles. The AV node regulates the propagation delay to the atrioventricular bundle (or “HIS” bundle). This coordination of the electrical activity of the heart causes atrial systole during ventricular diastole. This, in turn, improves the mechanical function of the heart. Atrial fibrillation occurs when anatomical obstacles in the heart disrupt the normally uniform propagation of electrical impulses in the atria. These anatomical obstacles (called “conduction blocks”) can cause the electrical impulse to degenerate into several circular wavelets that circulate about the obstacles. These wavelets, called “reentry circuits,” disrupt the normally uniform activation of the left and right atria. Because of a loss of atrioventricular synchrony, the people who suffer from atrial fibrillation and flutter also suffer the consequences of impaired hemodynamics and loss of cardiac efficiency. They are also at greater risk of stroke and other thromboembolic complications because of loss of effective contraction and atrial stasis.
One surgical method of treating atrial fibrillation by interrupting pathways for reentry circuits is the so-called “maze procedure” which relies on a prescribed pattern of incisions to anatomically create a convoluted path, or maze, for electrical propagation within the left and right atria. The incisions direct the electrical impulse from the SA node along a specified route through all regions of both atria, causing uniform contraction required for normal atrial transport function. The incisions finally direct the impulse to the AV node to activate the ventricles, restoring normal atrioventricular synchrony. The incisions are also carefully placed to interrupt the conduction routes of the most common reentry circuits. The maze procedure has been found very effective in curing atrial fibrillation. However, the maze procedure is technically difficult to do. It also requires open heart surgery, and is very expensive. Thus, despite its considerable clinical success, only a few maze procedures are done each year.
Maze-like procedures have also been developed utilizing catheters and/or surgical probes (collectively “probes”) that form lesions to create a maze for electrical conduction in a predetermined path. Typically, the lesions are formed by ablating tissue with one or more electrodes. Electromagnetic radio frequency (“RF”) energy applied by the electrode heats, and eventually kills (i.e. “ablates”), the tissue to form a lesion. During the ablation of soft tissue (i.e. tissue other than blood, bone and connective tissue), tissue coagulation occurs and it is the coagulation that kills the tissue. Thus, references to the ablation of soft tissue are necessarily references to soft tissue coagulation. “Tissue coagulation” is the process of cross-linking proteins in tissue to cause the tissue to jell. In soft tissue, it is the fluid within the tissue cell membranes that jells to kill the cells, thereby killing the tissue.
Catheters used to create lesions typically include a relatively long and relatively flexible body that has one or more electrodes on its distal portion. The portion of the catheter body that is inserted into the patient is typically from 23 to 55 inches in length and there may be another 8 to 15 inches, including a handle, outside the patient. The proximal end of the catheter body is connected to the handle which includes steering controls. The length and flexibility of the catheter body allow the catheter to be inserted into a main vein or artery (typically the femoral artery), directed into the interior of the heart, and then manipulated such that the electrode contacts the tissue that is to be ablated. Fluoroscopic imaging is used to provide the physician with a visual indication of the location of the catheter. Exemplary catheters are disclosed in U.S. Pat. No. 5,682,609.
Surgical probes used to create lesions often include a handle, a relatively short shaft that is from 4 inches to 18 inches in length and either rigid or relatively stiff, and a distal section that is from 1 inch to 10 inches in length and either malleable or somewhat flexible. One or more electrodes are carried by the distal section. Surgical probes are used in epicardial and endocardial procedures, including open heart procedures and minimally invasive procedures where access to the heart is obtained via a thoracotomy, thoracostomy or median sternotomy. Exemplary surgical probes are disclosed in U.S. Pat. No. 6,142,994.
Clamps, which have a pair of opposable rigid clamp members that may be used to hold a bodily structure or a portion thereof, are used in many types surgical procedures. Lesion creating electrodes have also been permanently secured to certain types of clamps. Examples of clamps which carry lesion creating electrodes are disclosed in U.S. Pat. No. 6,142,994. Such clamps are particularly useful when the physician intends to position electrodes on opposite sides of a body structure.
As used herein, the term “clamp” includes, but is not limited to, clamps, clips, forceps, hemostats, and any other surgical device that includes a pair of opposable clamp members that hold tissue, at least one of which is movable relative to the other. In some instances, the rigid clamp members are connected to a scissors-like arrangement including a pair of handle supporting arms that are pivotably connected to one another. The clamp members are secured to one end of the arms and the handles are secured to the other end. The clamp members come together as the handles move toward one another. Certain clamps that are particularly useful in minimally invasive procedures also include a pair of handles and a pair of clamp members. Here, however, the clamp members and handles are not mounted on the opposite ends of the same arm. Instead, the handles are carried by one end of an elongate housing and the clamp members are carried by the other. A suitable mechanical linkage located within the housing causes the clamp members to move relative to one another in response to movement of the handles.
The rigid clamp members in conventional clamps may be linear or have a predefined curvature that is optimized for a particular surgical procedure or portion thereof. It is, therefore, necessary to have a wide variety of clamps on hand. In the field of electrophysiology, a wide variety of clamps that have electrodes permanently secured thereto must be kept on hand.
The inventor herein has determined that it would be advantageous to provide physicians with a wide variety of devices, including clamps (both with and without energy transmission devices) and surgical probes that carry energy transmission devices, in a wide variety of shapes, and to do so in a manner that is more cost effective than conventional apparatus.